1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member. More particularly, the present invention relates to an electrophotographic photosensitive member containing a specific compound and a specific resin. The present invention further relates to an electrophotographic apparatus, a device unit, and a facsimile machine employing the above electrophotographic photosensitive member.
2. Related Background Art
In recent years, electrophotographic photosensitive members utilizing an organic material have come to be widely employed in copying machines and printers, and active research and development of the organic materials are going on.
Among the materials, especially oxytitanium phthalocyanines are attracting attention. Oxytitanium phthalocyanine is highly useful as a photosensitive material for electrophotographic printers and digital copying machines utilizing LED or semiconductor laser as the light source, since the oxytitanium phthalocyanine is highly sensitive to having a light wavelength ranging from about 600 nm to about 800 nm.
The electrophotographic photosensitive member employing oxytitanium phthalocyanine, however, has a disadvantage in spite of its high sensitivity, which is the relatively high residual potential under certain operating conditions. For example, when oxytitanium phthalocyanine is used in combination with a charge-transporting material, the ionization potential of the oxytitanium phthalocyanine is lower than that of conventional charge-transporting material. This is one reason why the carrier injection is not sufficient in the region of low electric field strength, and thereby the residual potential becomes high. An electrophotographic photosensitive member having such characteristics tends to give insufficient potential contrast in a electrophotographic system at a high processing speed or at a short process cycle, or in a system of laser beam exposure with a small laser spot. Furthermore, in such an electrophotographic photosensitive member, latitude for design of components is inevitably smaller as to the constitutions other than of oxytitanium phthalocyanine, such as in a charge-transporting layer, an intermediate layer, and surface-protection layer.
With the recent demand for high quality images and high durability of photosensitive members, electrophotographic photosensitive members being studied for higher sensitivity and better electrophotographic characteristics in repeated use.